Vapor production device and cooker with the same

ABSTRACT

A steam generating apparatus  20  including: a vaporizing container  1;  a heater  2  for heating the vaporizing container  1;  a feed pump  5  for feeding water from a reservoir tank  7  into the vaporizing container  1;  a drain valve  6  for draining water out of the vaporizing container  1  through a drain pipe  8;  a temperature detecting means  9  for detecting temperature of the vaporizing container  1;  and a controller  10  for controlling the heater  2,  the feed pump  5,  the drain valve  6,  and the like. After completion of steam generating operation, water remaining inside the vaporizing container  1  is drained after the temperature of the vaporizing container  1  has lowered to 60° C.

TECHNICAL FIELD

The present invention relates to a steam generating apparatus that heatsand humidifies a heating target by using steam. The present inventionalso relates to a heating cooker incorporating such a steam generatingapparatus.

BACKGROUND ART

Conventionally, a steam generating apparatus that uses steam and that isdesigned for use in a humidifying air conditioner or a humidifyingcooker is so constructed as to supply steam in the following manner:water fed from a reservoir tank is vaporized in a vaporizing containerheated with a heater or the like.

In such a steam generating apparatus, as time passes, substances, suchas calcium, dissolved in the water fed from the reservoir tank arecondensed inside the vaporizing container until eventually, when theirconcentrations become higher than their solubility, they are depositedin the form of scale. This may clog the steam outlet, or may attach tothe interior wall surface of the vaporizing container, leading todiminished vaporizing performance.

Patent Publication 1 listed below discloses, with a view to overcomingsuch clogging and diminishing of vaporizing performance due to scale, aconstruction in which the water left in the vaporizing container isdrained out of it and the vaporizing container is then heated and boiledwith no water in it (empty-boiled) for a predetermined length of time.This permits the scale to be forcibly removed from the vaporizingcontainer thanks to the difference in thermal expansion coefficientbetween them.

Patent Publication 1: Japanese Patent Application Laid-Open No.H5-231604

DISCLOSURE OF THE INVENTION

Problems to be Solved by the Invention

The conventional construction mentioned above requires empty-boiling fora predetermined length of time, resulting in extra consumption ofenergy. Moreover, since water remains evenly attached to the wallsurface of the vaporizing container after it has been drained, when thevaporizing container is empty-boiled, the water attached thereto isdried at high temperature. Drying water at high temperature in this waycauses the scale to crystallize to form hard, layered scale, whichfirmly attaches to the vaporizing container. Even if removed byexploiting the difference in thermal expansion coefficient, this layeredscale is hard and thus forms large fragments, which are likely to clogthe drain pipe or the drain valve and are difficult to remove. Whenclogging occurs, the steam generating apparatus cannot satisfactorilydeliver its performance.

An object of the present invention is to provide a steam generatingapparatus in which the scale attached to the inside of the vaporizingcontainer is made to form small fragments and the crystal growth of thescale is minimized so that it attaches less firmly to the vaporizingcontainer so as to be easily disposed of with a current of water.

Means for Solving the Problem

To achieve the above object, according to the present invention, a steamgenerating apparatus is provided with: a vaporizing container; heatingmeans for heating the vaporizing container; water feeding means forfeeding water into the vaporizing container; draining means for drainingwater out of the vaporizing container; temperature detecting means fordetecting the temperature of the vaporizing container; controlling meansfor controlling the heating means, the water feeding means, the drainingmeans, etc. Here, after the completion of steam generating operation,the water remaining inside the vaporizing container is drained after thetemperature of the vaporizing container has lowered to a predeterminedtemperature.

In this construction, an ample amount of water is kept present insidethe vaporizing container until its temperature has lowered to apredetermined temperature or less. Thus, water dries mainly on thesurface of the water, and not on the wall surface. After the water isdrained, the water that has attached to the wall surface of thevaporizing container starts to dry; here, the water dries below thepredetermined temperature. This minimizes the growth of scale, and thescale that has already deposited readily comes off and collects in thebottom of the container when the apparatus is operated next time. Thecollected scale is removed when water is drained after the completion ofoperation.

The predetermined temperature is set at 60° C. or less. Drying water ata temperature higher than 60° C. greatly prompts the crystallization ofscale. Thus, keeping an ample amount of water until the temperaturelowers to 60° C. or less helps minimize the crystallization of scale.

Alternatively, control may be so performed that, immediately after thecompletion of heating, first the water remaining inside the vaporizingcontainer is drained, and then water is fed into the vaporizingcontainer. At the end of heating, the temperature of the water insidethe vaporizing container is close to 100° C. Thus, first draining thishot water and then feeding ordinary-temperature water makes it possibleto lower the temperature of the vaporizing container in a shorter time.

As described above, at the end of heating, the temperature of thevaporizing container is 100° C. or more, and the temperature of thewater remaining inside the vaporizing container is close to 100° C.Thus, it takes time for these temperatures to lower to the predeterminedtemperature or less. By forcibly cooling the vaporizing container with acooling fan, it is possible to further reduce the time required to reachthe predetermined temperature.

In this case, a predetermined amount of water may be additionally fedinto the vaporizing container. With this construction, thanks to theeffect of the cooling fan combined with the additional feeding ofordinary-temperature water into the vaporizing container, it is possibleto still further reduce the time required for the vaporizing containerto reach the predetermined temperature.

ADVANTAGES OF THE INVENTION

In a steam generating apparatus according to the present invention,after the completion of steam generating operation, the vaporizingcontainer is cooled so that water is drained after the temperature ofthe vaporizing container has lowered to a predetermined temperature.This permits the water left attached to the wall surface of thevaporizing container after it has been drained to dry below thepredetermined temperature. This minimizes the crystallization of scale,allowing the scale to attach less firmly to the vaporizing container.Thus, the attached scale readily comes off and collects in the bottom ofthe container when the apparatus is operated next time. The collectedscale is removed when water is drained after the completion ofoperation. In this way, it is possible to prevent clogging and thediminishing of vaporizing performance.

BRIEF DESCRIPTION OF DRAWINGS

[FIG. 1] is an outline sectional view of the steam generating apparatusof a first embodiment of the invention.

[FIG. 2] is a flow chart showing an example of the operation of thesteam generating apparatus above.

[FIG. 3] is an outline sectional view of the steam generating apparatusof a second embodiment of the invention.

[FIG. 4] is a flow chart showing an example of the operation of thesteam generating apparatus above.

[FIG. 5] is a flow chart showing an example of the operation of thesteam generating apparatus of a third embodiment of the invention.

[FIG. 6] is an outline sectional view of the steam generating apparatusof a fourth embodiment of the invention.

[FIG. 7] is a flow chart showing an example of the operation of thesteam generating apparatus above.

[FIG. 8] is an outline sectional view of a heating cooker incorporatinga steam generating apparatus embodying the invention.

LIST OF REFERENCE SYMBOLS

1 Vaporizing Container

2 Heater

3 Steam Outlet

4 Feed/Drain Pipe

5 Feed Pump

7 Reservoir Tank

6 Drain Valve

8 Drain Pipe

9 Thermistor

10 Controller

11 Cooling Fan

12 Level Sensor

20 Steam Generating Apparatus

BEST MODE FOR CARRYING OUT THE INVENTION

A first embodiment of the present invention will be described below.FIG. 1 is an outline sectional view of the steam generating apparatus 20of the first embodiment of the invention. A vaporizing container 1 has aheater 2 fitted around the outside thereof. The vaporizing container 1is connected, at the top, to a steam outlet 3. The vaporizing container1 is connected, at the bottom, to a feed/drain pipe 4 and then through afeed pump 5 to a reservoir tank 7. When the feed pump 5 is started, thewater inside the reservoir tank 7 is fed through the feed/drain pipe 4into the vaporizing container 1. The feed/drain pipe 4 is also connectedto a drain pipe 8. When the drain valve 6 is opened, the water insidethe vaporizing container 1 is drained out of it through the drain pipe8. Near the heater 2, a thermistor 9 is provided as a temperaturedetecting means. A controller 10 monitors the temperature of thevaporizing container 1, and controls the operation of the feed pump 5.The drain valve 6 is realized with a solenoid- or motor-operated valvethat can be opened and closed electrically. Thus, the controller 10 canalso control the opening and closing of the drain valve 6.

Now, the operation of the steam generating apparatus 20 constructed asdescribed above will be described with reference to the flow chart shownin FIG. 2. The water inside the vaporizing container 1 is heated andboiled by the heater 2. In the space in an upper portion of thecontainer, steam is separated so as to be fed out through the steamoutlet 3. On completion of the steam generating operation, the heater 2is turned off (step S1), and the monitoring of the temperature of thevaporizing container 1 by the thermistor 9 is started (step S2). Thestate as it currently is, i.e., with an ample amount of water presentinside the vaporizing container 1, is maintained until the temperatureof the vaporizing container 1 lowers to a predetermined temperature.Next, when the thermistor 9 detects the predetermined temperature, thecontroller 10 immediately opens the drain valve 6 (step S3), so that thewater inside the vaporizing container 1 is drained out of it through thedrain pipe 8. Thus, the water that has attached to the interior wallsurface of the vaporizing container 1 dries below the predeterminedtemperature. This minimizes the crystallization of scale.

Next, a second embodiment of the present invention will be described.FIG. 3 is an outline sectional view of the steam generating apparatus 20of the second embodiment of the invention. In this figure, such membersas are found also in the steam generating apparatus of the firstembodiment described above are identified with common referencenumerals, and their explanations will not be repeated. Here, a coolingfan 11 is additionally provided for cooling the vaporizing container 1and the heater 2. The operation of the cooling fan 11 is controlled bythe controller 10.

Now, the operation of the steam generating apparatus 20 constructed asdescribed above will be described with reference to the flow chart shownin FIG. 4. On completion of the steam generating operation, the heater 2is turned off (step S4), and in addition the cooling fan 11 is started(step S5) so as to start to cool the vaporizing container 1 and theheater 2. Moreover, the monitoring of the temperature of the vaporizingcontainer 1 by the thermistor 9 is started (step S6). The state as itcurrently is, i.e., with an ample amount of water present inside thevaporizing container 1, is maintained until the temperature of thevaporizing container 1 lowers to a predetermined temperature. Next, whenthe thermistor 9 detects the predetermined temperature, the controller10 immediately stops the cooling fan 11 (step S7) and opens the drainvalve 6 (step S8), so that the water inside the vaporizing container 1is drained out of it through the drain pipe 8. Thus, the water that hasattached to the interior wall surface of the vaporizing container 1dries below the predetermined temperature. This minimizes thecrystallization of scale. With the construction of this embodiment, theuse of the cooling fan 11 helps reduce the time required up till thewater is drained.

Next, a third embodiment of the present invention will be described.Here, the steam generating apparatus 20 has the same outlineconstruction as shown in FIG. 3.

Now, the operation of the steam generating apparatus 20 of thisembodiment will be described with reference to the flow chart shown inFIG. 5. On completion of the steam generating operation, the heater 2 isturned off (step S9), and in addition the cooling fan 11 is started(step S10) to start to cool the vaporizing container 1 and the heater 2.Moreover, the feed pump 5 is started to start to feed additional waterfrom the reservoir tank 7 into the vaporizing container 1 (step S11).Additional water is fed for a predetermined length of time to cool thevaporizing container 1 (steep S12). When the predetermined length oftime has elapsed, the feed pump 5 is stopped (step S13), and themonitoring of the temperature of the vaporizing container 1 by thethermistor 9 is started (step S14). The state as it currently is, i.e.,with an ample amount of water present inside the vaporizing container 1,is maintained until the temperature of the vaporizing container 1 lowersto a predetermined temperature. Next, when the thermistor 9 detects thepredetermined temperature, the controller 10 immediately stops thecooling fan 11 (step S15) and opens the drain valve 6 (step S16), sothat the water inside the vaporizing container 1 is drained out of itthrough the drain pipe 8. Thus, the water that has attached to theinterior wall surface of the vaporizing container 1 dries below thepredetermined temperature. This minimizes the crystallization of scale.In this embodiment, the feeding of additional water by the feed pump 5helps further reduce the time required to cool the vaporizing container1.

Next, a fourth embodiment of the present invention will be described.FIG. 6 is an outline sectional view of the steam generating apparatus 20of the fourth embodiment of the invention. In this figure, such membersas are found also in the steam generating apparatuses of the first,second, and third embodiments described above are identified with commonreference numerals, and their explanations will not be repeated. Here, alevel sensor 12 is additionally provided that detects the water levelinside the feed/drain pipe 4 and thereby permits the detection of thedrainage state of the vaporizing container 1. This detection isperformed by the controller 10.

Now, the operation of the steam generating apparatus 20 constructed asdescribed above will be described with reference to the flow chart shownin FIG. 7. On completion of the steam generating operation, the heater 2is turned off (step S17), and in addition the cooling fan 11 is started(step S18) to start to cool the vaporizing container 1 and the heater 2.Moreover, the drain valve 6 is opened to start to drain the waterremaining inside the vaporizing container 1 out of it (step S19). Thelevel sensor 12 monitors the water level inside the feed/drain pipe 4(step S20), and, when it detects the completion of the drainage, thedrain valve 6 is closed (step S21), and immediately the feed pump 5 isstarted to start to feed additional water from the reservoir tank 7 intothe vaporizing container 1 (step S22). Additional water is fed for apredetermined length of time (step S23), and then the feed pump 5 isstopped (step S24). Now, the monitoring of the temperature of thevaporizing container 1 by the thermistor 9 is started (step S25). Thestate as it currently is, i.e., with an ample amount of water presentinside the vaporizing container 1, is maintained until the temperatureof the vaporizing container 1 lowers to a predetermined temperature.Next, when the thermistor 9 detects the predetermined temperature, thecontroller 10 immediately stops the cooling fan 11 (step S26) and opensthe drain valve 6 (step S27), so that the water inside the vaporizingcontainer 1 is drained out of it through the drain pipe 8. Thus, thewater that has attached to the interior wall surface of the vaporizingcontainer 1 dries below the predetermined temperature. This minimizesthe crystallization of scale. In this embodiment, immediately after thecompletion of steam generating operation, first the hot water remaininginside the vaporizing container 1 is drained, and then additional wateris fed into it by the feed pump 5. This helps reduce the time requiredto cool the vaporizing container 1.

FIG. 8 shows the construction of a heating cooker incorporating a steamgenerating apparatus 20 embodying the invention. The water fed from thereservoir tank 7 into the vaporizing container 1 is converted into steaminside the vaporizing container 1, and is then fed into a heatingcompartment 14, in which a cooking target 13 is placed, to cook thecooking target 13.

INDUSTRIAL APPLICABILITY

Steam generating apparatuses according to the present invention findapplication in, for example, steam-heating cookers, i.e., heatingcookers that cook a cooking target by application of heat thereto thatis achieved by feeding steam into a heating chamber.

1. A steam generating apparatus comprising: a vaporizing container; heating means for heating the vaporizing container; water feeding means for feeding water into the vaporizing container; draining means for draining water out of the vaporizing container; temperature detecting means for detecting temperature of the vaporizing container; controlling means for controlling the heating means, the water feeding means, and the draining means, wherein, after completion of steam generating operation, water remaining inside the vaporizing container is drained after the temperature of the vaporizing container has lowered to a predetermined temperature.
 2. The steam generating apparatus of claim 1, wherein after completion of steam generating operation, the water remaining inside the vaporizing container is drained, and in addition water is fed into the vaporizing container.
 3. The steam generating apparatus of claim 1, further comprising: a cooling fan for forcibly cooling the vaporizing container.
 4. The steam generating apparatus of claim 3, wherein, when the vaporizing container is forcibly cooled by the cooling fan, water is additionally fed into the vaporizing container by the water feeding means.
 5. A heating cooker comprising the steam generating apparatus of claim
 1. 6. A heating cooker comprising the steam generating apparatus of claim
 2. 7. A heating cooker comprising the steam generating apparatus of claim
 3. 8. A heating cooker comprising the steam generating apparatus of claim
 4. 